Potters often use pottery wheels to make the pottery. Wheel made pottery requires the clay to be centered on the rotating wheel before the pottery can be formed into a particular shape. After the piece of pottery is made, the piece must be recentered for trimming, final shaping, and decorating. To facilitate productivity, attachments are often used. The attachments include bats, trimming apparatuses, and fixtures to hold the pottery during fabrication, trimming, shaping and decorating.
Currently, there are a variety of mechanical methods used to mount these attachments on a pottery wheel, also called a wheel head. Two of the most common are ¼-20 hex-head screws that are mounted into ¼ inch holes drilled nominally at standard locations in the pottery wheel, and ears that clamp to the sides of the pottery wheels. Unfortunately wheel manufacturers do not precisely locate the holes in the same location, nor do they machine the wheel heads to precisely the same diameter. Also, there are multiple wheel manufacturers with varying tolerances and multiple methods for mounting the wheel head to the axle around which it rotates. Each accessory must, therefore, be adjusted by a potter to fit each wheel in a pottery studio on which it is used. This essentially limits the use of bats and trimming accessories to exclusive use on one wheel. Thus, for both methods, the attachments are only applicable to a one wheel head due to the variation in the hole location, the wheel head diameter from wheel head to wheel head, and manufacturing variations.
Because the holes in the wheel head may not be located precisely and the edge of the wheel head may not be concentric with the rotating axis, accessories cannot recenter the work piece without some method to adjust the location of the accessory to compensate for the variations in the location of the holes or the edge of the wheel head. Attachment manufacturers initially used holes drilled into the accessories at the approximate location of the holes in the wheel head. The holes were then aligned with the heads of the bolts mounted on the pottery wheel. One hole was made substantially oval-shaped to accommodate the variation in the hole location.
Often the work takes longer than one session and/or when completed needs to remain undisturbed until it dries. In such a situation, it is advantageous to be able to remove the completed or partially completed work from the wheel so that wheel may be used for other work. In such situations accessories called bats may be used. Bats are flat round trays, usually the size of the pottery wheel, which may be removed from, and remounted on, the pottery wheel. To use such a bat, the pottery wheel may have holes drilled nominally at predetermined locations. Locating pins are mounted in the holes. The bat has holes at locations corresponding to those of the locating pins on the pottery wheel. Before beginning work which will require several sessions, the potter mounts the bat on the pottery wheel. The locating pins hold the bat on the pottery wheel. The work is then performed on top of the bat. When the session is over, the bat, with the completed or partially completed work-piece on it, is lifted off the wheel. The wheel, thus, becomes available for different work.
Bats made from non-porous material, e.g. plastic or masonite bats, are currently available. To use these bats, the pottery wheel has holes drilled at points nominally along a diameter at a radius of, for example, 5 inches. Bolts having a specified head size, e.g. ¼-20 hex-head bolts, are commonly mounted in the holes. The non-porous bat has holes in it, at nominal locations corresponding to the locations of the bolts: i.e. also along a diameter and at a radius of 5 inches. The size of these holes is slightly larger than the size of the bolt heads. In a specific non-porous bat, one hole is round while the other is oval-shaped. The bat, thus, may be mounted on and removed from the pottery wheel as work on the work-piece progresses. Because the holes in the pottery wheel are not precisely at the nominal locations, the remounted non-porous bat may not be at precisely the same location on the pottery wheel and, thus, may not be centered. This is especially true if the non-porous bat is mounted on a different pottery wheel.
Porous bats, such as those made from plaster, provide advantages that non-porous bats do not. For example, a work-piece on a non-porous bat will begin to dry from the outside surfaces, except the surface on the non-porous bat. This leads to uneven drying. A porous bat, on the other hand, absorbs water so all surfaces of the work-piece, including that against the bat, will dry allowing the work-piece to dry more evenly. Also, because the porous bat absorbs the moisture, the potter will be able to release the work-piece from the bat without having to cut it off with a wire.
Plaster bats, more specifically, are easy and economical to fabricate, and a potter may make as many plaster bats as needed by constructing a dam around the edge of the pottery wheel, e.g. by using wide tape or clay. The resulting volume is filled with plaster. When the plaster sets, the dam is removed and the bat may be used. The bat may be attached to the pottery wheel using clay as an adhesive between the top of the pottery wheel and the bottom of the bat. This requires that the bat be recentered manually whenever it is remounted on the pottery wheel.
Some attempts have been made to allow a plaster bat to use the same attachment mechanism as described above with respect to the non-porous bats. For example, as described above, bolts may be mounted in holes drilled in the pottery wheel, then the plaster for the bat poured. When the plaster has set, it will fit atop the bolts and not require clay as an adhesive or manual recentering. Bats are also made commercially in this manner, sometimes using rubber grommets. However, because the holes in the pottery wheel are not located precisely, a commercially produced bat may not fit onto the bolts in the pottery wheel.
This solution also may not work if there is more than one pottery wheel on which the bat may be placed. Although manufacturers of pottery wheels may drill the holes in the pottery wheel, it is often the case that potters drill the holes in their own wheels. Further, even when the manufacturer drills the holes, they are not drilled with precision. In either case, the locations of the holes may vary relatively widely from one pottery wheel to another. This is not a problem with non-porous bats because, as described above, they are manufactured with one round hole and one oval-shaped hole.
However, as described above, plaster bats may be fabricated directly on the pottery wheel, or commercially with rubber grommets. If the locating pins on a pottery wheel do not align precisely with the corresponding holes in the bat, the bat does not fit on that pottery wheel. Even if the bat fits on the pottery wheel, the holes in this pottery wheel may not be in the same relative locations with respect to the center of the original pottery wheel, thus, the bat may not be centered on the new pottery wheel. In addition, plaster is soft and brittle. Repeatedly removing and remounting a plaster bat made as described above on a pottery wheel, even the pottery wheel on which is was originally fabricated, eventually leads to the bolt heads scraping the holes in the bat, making them larger and allowing the bat to slip on the pottery wheel.